In current wireless communication systems such as an LTE (Long Term Evolution), MIMO (Multiple Input Multiple Output) technologies have been widely used. In the MIMO technologies, precoding is an important step, and a precoding process is a process for mapping transmitted data to transmitting antennas in a certain manner, of which the purpose lies in enabling a terminal to acquire better received signal quality via such processing. In an application scenario of the MIMO, one of the functions of the precoding is to decrease signal interferences between users. A conventional precoding scheme can be divided into two types: linear precoding and non-linear precoding. The precoding process is completed at a base station side, and most precoding schemes require the base station to acquire downlink channel state firstly, and then utilize the downlink channel state to complete a precoding operation.
When acquiring the downlink channel state, the operating mode of a communication system, including a TDD (Time Division Duplexing) mode and an FDD (Frequency Division Duplexing) mode needs to be considered. In the TDD mode, as long as a time interval between uplink and downlink is less than channel coherence time, the base station can acquire downlink channel state according to estimated uplink channel state, but that's not to say that the downlink channel state can be acquired according to the estimated uplink channel state as long as in the TDD mode. When unable to acquire the downlink channel state according to the estimated uplink channel state, a method for acquiring downlink channel state in the TDD mode is the same as a method for acquiring downlink channel state in the FDD mode. In the FDD mode, a downlink channel needs to be measured via a terminal side, and a codeword which best represents estimated results of the downlink channel state is selected from a predesigned codebook according to measurement results, where one codebook consists of limited codewords and each codeword represents a class of downlink channel state. An index of the selected codeword is fed back to a base station, the base station selects the same codeword in the same codebook according to the codeword index, and utilizes the codeword to complete a precoding operation.
At least the following problems exist in the prior art: in the current LTE system, there is only a codebook for the linear precoding scheme, and there is no codebook for the non-linear precoding scheme. When the system needs to have both precoding schemes simultaneously, the base station cannot acquire a corresponding codeword according to different precoding schemes, and cannot acquire state information of the downlink channel.